Trailer articulation angle estimation

ABSTRACT

This invention takes the advantage of existing radar, vision and ultrasonic sensors available for side blind spot detection, rear view, rear virtual bumper, and rear parking assist. Using a sensor fusion technique to combine the useful information from these sensors, the trailer articulation angles as well as trailer track width and tongue length is accurately estimated. When an active steering system is present, vehicle and trailer can be controlled with increased stability by applying the trailer information.

TECHNICAL FIELD

This invention is related generally to vehicle stability. Moreparticularly, the invention is concerned with the traveling stability ofa combination comprising a motorized vehicle and a load that is attachedthereto, such as a trailer.

BACKGROUND OF THE INVENTION

Many motorized vehicles are designed to accommodate the towing ortrailering of various loads, including without limitation: cargohoppers, campers, boats, and sometimes other motorized vehicles. A widerange of systems and devices to enhance vehicle stability while towingis known. These devices may include simple add-ons such as airfoils andother vehicle trim pieces such as ground effects, which confer thevehicle with additional aerodynamic stability over its design control.Additionally, systems for traction control have been developed, as wellas automatically-adjusting suspension systems which alter the height ofthe body of a vehicle in proportion to the weight of a load.

It often occurs that trailer design changes are made by engineers duringthe course of trailer design, without regard to the overall effect oftheir design changes may have on the stability of every possiblevehicle/trailer combination of which their trailer is to be a part.Thus, it is natural that some vehicle/trailer combinations may beinherently more stable at highway speeds than others, and there is ingeneral no way to reasonably predict the behavior of all such possiblecombinations, when faced with various challenging road situations, suchas crosswinds, etc., prior to an actual road test.

It is known to mount sensors on the rear and side of vehicles to detectobjects behind a vehicle for active safety features, such as visionsensors used for rear view and side blind zone object detection, andalso radar sensors for side blind zone detection, rear object detection,and rear cross traffic detection. Ultrasonic sensors are often presenton vehicles for assistance in rear parking maneuvers.

One of the major enablers for the development of a vehicle and trailerstability control system is the availability of a hitch angle sensorwhich can be independent of the trailer connected. A remote hitch anglesensing system is a key enabler for a low cost vehicle-trailer stabilitycontrol. There are several known contact type hitch angle sensors whichhave been used for such application. However, these contact type sensorsare cumbersome since trailers are frequently connected and disconnected,and a new calibration and adjustment is necessary following each suchconnection cycle.

In a general sense, it is desirable to provide systems having increaseddegree of reliability and integrity for aiding vehicle/trailercombinations than what has been previously available. One shortfall fortrailer control systems has been the sensing of the trailer hitcharticulation angle for a trailer control system. There remains a need inthe art for utilization of the output of the aforementioned sensors inan improved synergistic fashion to provide greater stability whiletraveling and to provide means for directional control invehicle/trailer backing and parking. The present systems and methodsprovide enhanced means for assisting in stabilizing vehicle/trailercombinations by providing a new and beneficial means for calculating thehitch articulation angle, using sensing means which are disposed solelyon the motorized vehicle used for towing.

SUMMARY OF THE INVENTION

The present invention provides a system useful for determining thetrailer hitch articulation angle of a trailer that is being towed behinda motorized vehicle. A system according to the invention employs sensingmeans which are disposed only on the motorized vehicle. The sensingmeans comprise one or more sensing means selected from: ultrasonictransducers, short-range radar transducers, and cameras. The sensingmeans comprise one or more sensing means selected from: ultrasonictransducers, short-range radar transducers, vision systems transducers,cameras and light-imaging detection and ranging transducers and systems(LIDAR).

The invention also provides a process for calculating the trailer hitcharticulation angle in a combination comprising a motorized vehiclehaving a trailer comprising a wheeled axle that is pivotally-connectedthereto. The motorized vehicle includes sensing means comprising one ormore of: ultrasonic transducers, short-range radar transducers, andcameras. A process according to the invention comprises the steps of: a)acquiring position and range information concerning the trailer by meansof the sensing means employed; b) conveying the position and rangeinformation to a microprocessor; c) calculating the trailer tonguelength of the trailer; d) calculating the track width of the trailer;and e) calculating the trailer hitch articulation angle of the trailer.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may take physical form in certain parts and arrangement ofparts, the embodiments of which are described in detail and illustratedin the accompanying drawings which form a part hereof, and wherein:

FIG. 1 shows an overhead view of a motorized vehicle having a trailerattached thereto;

FIG. 2 shows an overhead schematic view showing pertinent parameters andangles present in a vehicle/trailer combination as shown in FIG. 1;

FIG. 3 shows a side elevation view of a motorized vehicle to which atrailer is pivotally-attached at a conventional fashion;

FIG. 4 shows an overhead schematic view of a vehicle/trailer combinationas shown in FIGS. 1 and 2, in which the trailer is disposed in aposition with its centerline forming an angle θ with respect to thecenterline of the motorized vehicle;

FIG. 5 shows an algorithm which is useful in the practice of a methodaccording to the invention; and

FIG. 6 shows a schematic of a processing scheme according to theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides a system for enhancement ofvehicle/trailer stability, by assessing and assisting of vehiclecontrol/trailer dynamics in real time, using one or more of a pluralityof sensors that are mounted on the vehicle only, as opposed to thesystems known in the prior art, that employ only trailer-mountedsensors.

According to the invention, parameters associated with the trailer, suchas hitch angle and trailer tongue length are estimated accurately inreal time for precise vehicle/trailer stability control, using onlyvehicle-mounted sensing means. The invention also provides a methodwhich includes sensing the trailer articulation angle, using a set ofsensors mounted on the rear and side of a vehicle to detect the positionof objects being towed behind the vehicle. Once these parameters areestimated and/or calculated, they are usefully employed in generatingaudible or visual warning signals, or in providing electronic feedbackto or within systems, methods and/or devices complementary to thepresent invention, including without limitation the systems and methodsdescribed in commonly assigned U.S. Pat. Nos. 6,838,979 and 6,999,856,each of which are herein incorporated by reference in their entirety. Byuse of the present invention, the need for a hitch articulation sensorcan be eliminated.

In order to enhance the shortcomings of sensors which are sometimesemployed in the prior art as the sole source of input in calculation ofa parameter such as a distance, the present invention applies a sensorfusion technique using information and/or outputs from more than asingle sensor, whereby, for example, the edge of a trailer can bedetected using vision and radar, and processed to estimate hitcharticulation angle and trailer tongue length. These parameters are theessential information necessary for trailer stability and parkingcontrol.

Referring now to the drawings, wherein the showings are for the purposeof illustrating the invention only and not for the purpose of limitingthe same, FIG. 1 shows an overhead view of a motorized vehicle 10 havinga trailer 12 attached thereto, by means of a conventional hitchingmeans, which includes a trailer tongue 25 pivotally connected at pivotalcoupling 27 to the trailer hitch 29 of motorized vehicle 10, as is knownin the art. The motorized vehicle 10 is preferably equipped with varioussensors, including short-range radar transducer 21, ultrasonic sensor23, steering-wheel angle sensor 11, yaw rate sensor 19, left side blindzone camera 15, and right side blind zone camera 17. There is a dataprocessor 13, which preferably comprises a microprocessor, into whichinformation gathered from each of the aforesaid sensors is inputted, forstorage, aggregation, and processing purposes, towards computation ofthe trailer hitch articulation angle θ, as explained further below.

FIG. 2 is an overhead schematic view of a vehicle/trailer combination asshown in FIG. 1, which further includes location and definition ofvarious physical parameters which are useful in a method and systemaccording to the invention, for calculating the angle θ, the trailerhitch articulation angle. These parameters include: L₁, the vehiclewheelbase dimension; h, the distance from the rear axle 33 of themotorized vehicle 10 to the pivotal coupling 27; and Lt, the distancefrom the pivotal coupling 27 to the centerline of an axle 31 of thetrailer 12. Lt is sometimes referred to as the trailer tongue length.Shown also is L2, which is the distance from the rear axle 33 of themotorized vehicle 10 to the end portion 35 of the body of the motorizedvehicle 10. Tt is one-half of the track width distance of an axle on thetrailer 12; Tv is one-half of the track of the motorized vehicle 10, andTm is the distance from the centerline of the motorized vehicle 10 tothe center of the left side blind zone camera 15. φv is the anglebetween the center of the left side blind zone camera 15 and the rearcorner portion of the body of the motorized vehicle 10 with respect tothe line of travel of the motorized vehicle 10 when it is travelingstraight, in the forward direction, and φt is the azimuth angle betweenthe center of the left side blind zone camera 15 and the wheel on anaxle of trailer 12, with respect to the line of travel of the motorizedvehicle/trailer combination when they are connected and are collectivelytraveling straight, in the forward direction. The parameter m is thedistance between the center of rotation of a front left wheel of themotorized vehicle 10, and the visual sensor of the left side blind zonecamera 15.

FIG. 3 is a side elevation view of a motorized vehicle 10 to which atrailer 12 is pivotally-attached at a conventional fashion. Theparameters L1, h, Lt and m are the same parameters defined in FIG. 2from the overhead view therein, and in FIG. 3 are further defined theparameters ψt and m_(h). ψt is the angle between the point at which thewheel of the trailer contacts a road surface S upon which the trailer 12resides, and a horizontal line H that is disposed substantially parallelto the road surface, which horizontal line H intersects the lens of theleft side blind zone camera 15. The parameter m_(h) is the verticalposition of the center of the side blind zone camera 15 from the groundS.

FIG. 4 is an overhead schematic view of a vehicle/trailer combination asshown in FIGS. 1 and 2, with the trailer being disposed in a positionwherein the centerline of the trailer 12 makes an angle θ with respectto the centerline of the motorized vehicle 10, which angle θ is referredto as the trailer articulation angle, with angle θ being of particularinterest and use in providing stability to a vehicle/trailer combinationaccording to a system and method of the invention. The relevantparameters again include: L₁; h; Lt; L2; Tt; Tv; Tm; φv; φt; and m,whose meanings have been defined above in reference to FIG. 2.

In seeking to calculate the trailer hitch articulation angle θ in realtime, it is helpful to consider the relation in FIG. 3:

$\begin{matrix}{\frac{m_{h}}{L_{1} - m + h + L_{t}} - {\tan \; \psi_{t}}} & (1)\end{matrix}$

which relates the known parameters of m, h, L₁, m_(h) and the measurableangle ψ_(t), to the trailer tongue length L_(t) ψ_(t) is obtained fromthe left side blind zone camera 15. However, the right side blind zonecamera 17 can be used to acquire similar data from the opposite side ofthe vehicle as shown in FIG. 3, owing to the general symmetry of thevehicle/trailer combination. In fact, all quantities discussed, whichare obtained by considering the left side of the vehicle/trailercombination are generally valid for the right side of thevehicle/trailer combination as well. Equation (1) can be re-arrangedthus:

$\begin{matrix}{L_{t} = {\frac{m_{h}}{\tan \; \psi_{t}} + m - h - {L_{1}.}}} & (2)\end{matrix}$

Once the trailer tongue length Lt is known, other pertinent parameterscan be calculated. It is beneficial to consider FIG. 2 and the relation:

$\begin{matrix}{\frac{T_{v} - T_{m}}{L_{1} - m + L_{t}} = {\tan \; \phi_{v}}} & (3)\end{matrix}$

in which all variables are known, as it relates to the vehicle.Similarly, from the consideration of the trailer, the expression:

$\begin{matrix}{\frac{T_{1} - T_{m}}{L_{1} - m + h + L_{t}} = {\tan \; \phi_{t}}} & (4)\end{matrix}$

can be derived, which rearranges to:

$\begin{matrix}{L_{t} = {\frac{T_{1} - T_{m}}{\tan \; \phi_{t}} - L_{1} + m - {h.}}} & (5)\end{matrix}$

Referring now to FIG. 4, an expression can be created which relates thetrailer hitch articulation angle θ to the values for the otherparameters, some of which were known and some of which were measured bythe side blind zone camera(s):

$\begin{matrix}{\frac{{L_{t}\sin \; \theta} + {T_{t}\cos \; \theta} - T_{m}}{L_{1} - m + h + {L_{t}\cos \; \theta} - {T_{t}\sin \; \theta}} = {\tan \; \phi_{t}}} & (6)\end{matrix}$

which simplifies to:

$\begin{matrix}{{\theta = {{\sin^{- 1}\left\lbrack \frac{T_{m} + {\left( {L_{1} - m + h} \right)\tan \; \phi_{t}}}{\sqrt{\left( {T_{t} - {L_{t}\tan \; \phi_{t}}} \right)^{2} + \left( {L_{t} + {T_{t}\tan \; \phi_{t}}} \right)^{2}}} \right\rbrack} - \delta_{t}}}{wherein}} & (7) \\{\delta_{t} = {{\sin^{- 1}\left\lbrack \frac{T_{t} - {L_{t}\tan \; \phi_{t}}}{\sqrt{\left( {T_{t} - {L_{t}\tan \; \phi_{t}}} \right)^{2} + \left( {L_{t} + {T_{t}\tan \; \phi_{t}}} \right)^{2}}} \right\rbrack}.}} & (8)\end{matrix}$

Thus, by the above relations, we are able to obtain the values for Ttand Lt from consideration of known distance parameters on the motorizedvehicle 10 and values obtained by the side blind zone cameras once thetrailer 12 is attached to the motorized vehicle 10. Computation of thetrailer hitch articulation angle may then be effected by carrying outthe necessary calculations outlined above, which is preferably done by adata processor 13 that is on-board of the motorized vehicle 10.Advantageously, a short-range radar transducer 21 or an ultrasonicsensor 23 mounted to the rear of the motorized vehicle 10 is beneficialfor providing instant measurement of the distance at which the forwardportion of the trailer 12 is disposed from such sensors, to augment thedata obtained from the side blind zone cameras. For example, the trailerarticulation angle may be derived per the foregoing discussion at aparticular point in time. There will be associated with a trailerarticulation at such particular point in time outputs from short-rangeradar transducer(s) and/or ultrasonic sensor(s) as they interact withsurfaces of the trailer 12 being towed, which outputs will depend on thespecific geometry of the exterior features of the trailer 12. Accordingto another embodiment, such output data from these sensors, which areassociated with each trailer hitch articulation angle θ derived usingthe side blind zone camera(s), are collected, stored, and associatedwith each trailer hitch articulation angle θ derived from the side blindzone cameras alone, so that the side blind zone cameras are no longernecessary in determining the trailer hitch articulation angle θ. Inanother embodiment, the distance Lt is obtained directly from ashort-range radar transducer mounted on the motorized vehicle 10. Inanother embodiment, the distance Lt is obtained directly from anultrasonic sensor mounted on the motorized vehicle 10.

FIG. 5 shows an algorithm (501) which is useful in the practice of amethod according to the invention. At the start, the sensors on boardthe motorized vehicle 12 search and detect for the presence of a trailer12. If no trailer is present, the system will continue to attempt tolocate a trailer (503). When a trailer 12 is present, the systemdetermines whether a trailer hitch articulation angle θ has yet beencalculated (505). If not, the system proceeds to determine whether themotorized vehicle/trailer combination is in motion (507). If there is nomotion, then the system waits (509) until the motorized vehicle/trailercombination are in motion at which time data are collected and initialvalues for Tt, Lt, and the azimuth angle φt are calculated (511, 513),and all the relevant values are used in calculation of an initialtrailer hitch articulation angle θ using equation (7) or an equivalentexpression (515). The process is repeated periodically to providecontinuous monitoring of the trailer hitch articulation angle θ.

FIG. 6 represents a schematic of a processing scheme according to onealternate embodiment of the invention. Shown is a controller 13 coupledto an associated memory unit 37. The controller 13 is coupled to asystem I/O module 35 which is configured to accept signals from thevarious vehicle on-board sensors 15, (17), 19, 21, 23 and includingother sensing means known in the art, including without limitation LIDARsensing transducers and systems. The I/O module 35 is coupled to aninterface 39, which may be a display that is readable by the driver ofthe motorized vehicle, or which interface 39 may alternately comprise acoupling that is fed as an input to an additional processor, asdescribed, to cite but one example, in U.S. Pat. No. 6,838,979, whosealgorithm may be used in providing an alarm as taught therein based onvalues for angle θ provided by the present invention. In yet anotheralternate embodiment, the interface 39 is connected to a servo-actuatorthat is mechanically linked to the steering control system of the motorvehicle. In yet another alternate embodiment, the interface 39 isconnected to a servo-actuator that is mechanically linked to the brakingsystem of the motor vehicle.

Thus, the systems and methods provided by the invention enableestimation of the articulation angle θ without any contact of anyportions of the trailer 12. Additionally, all sensors are on themotorized vehicle 10. A system according to the invention isself-calibrating and self-correcting, in real time and usesreadily-available sensors.

While the invention has been described by reference to certainembodiments, it should be understood that changes can be made within thespirit and scope of the inventive concepts described. Accordingly, it isintended that the invention not be limited to the disclosed embodiments,but that it have the full scope permitted by the language of thefollowing claims.

1. A system useful for determining the trailer hitch articulation angleof a trailer that is being towed behind a motorized vehicle, comprising:at least one non-contacting sensor disposed only on the motorizedvehicle; said at least one sensor having an output signal coupled to adata processor, wherein said data processor calculates the trailer hitcharticulation angle based on the output signal of said at least onesensor.
 2. A system according to claim 1 wherein said at least onesensor comprises at least one of ultrasonic transducers, short-rangeradar transducers, LIDAR sensors, cameras and combinations thereof.
 3. Asystem according to claim 1 wherein said at least one sensor comprises acamera and an ultrasonic transducer.
 4. A system according to claim 1wherein said at least one sensor comprises a camera and a short-rangeradar transducer.
 5. A system according to claim 1 wherein said dataprocessor is connected to an I/O unit.
 6. A system according to claim 5wherein said one or more sensing means are connected to said dataprocessor through said I/O unit.
 7. A system according to claim 6further comprising an interface connected to said I/O unit.
 8. A systemaccording to claim 1 further comprising a steering-wheel angle sensorhaving an output which is inputted into said data processor.
 9. A systemaccording to claim 1 further comprising a yaw rate sensor having anoutput which is inputted into said data processor.
 10. A process forcalculating the trailer hitch articulation angle in a combinationcomprising a motorized vehicle having a trailer comprising a wheeledaxle that is pivotally-connected thereto, said motorized vehicleincluding at least one non-contacting sensor, said process comprising:acquiring trailer position and range information from said at least onenon-contacting sensor; conveying said information to a microprocessor;determining the trailer tongue length of said trailer from theinformation acquired from said at least one non-contacting sensor;determining the track width of said trailer from the informationacquired from said at least one non-contacting sensor; and calculatingthe trailer hitch articulation angle of said trailer based on thedetermined trailer tongue length and determined track width.
 11. Aprocess according to claim 10 wherein a camera is employed as said atleast one non-contacting sensor, and said trailer position and rangeinformation includes the azimuth angle between the center of the cameraon said vehicle and the wheel on said axle of said trailer.
 12. Aprocess according to claim 10 wherein a camera having a lens is employedas said at least one non-contacting sensor, and said trailer positionand range information includes the angle between the point at which awheel of the trailer contacts a road surface upon which the trailerresides and a horizontal line disposed substantially parallel to theroad surface, which horizontal line intersects the lens of said camera.